Dick,
It really depends on what you want to do, I guess. I have always used
the same motor in both classes. I just build for Gas Class and accept
that it will be a little less effective on Fuel.
We run about 12.5:1 compression, I have found that it gets real
difficult to get much more than 13:1 in a 302 cu in Chevrolet motor. We
do well on Alky, better when adding nitrous, and have run 33% nitro with
good success in the 1/4 and 1/2 mile drags. In 1967, we ran 190 MPH at
El Mirage in D/FR, at that time we held the D/GR record at 173.74 MPH.
That was as far as I could run the engine on nitro without major
problems, it was detonating severely at the end of the run. My best time
at Bonneville on nitro was 196, I could never make it live past the 1
1/2 mile with all cylinders running. It was surely a great ride while it
lasted.
I was running a basic gasoline setup, just changing nozzles and jet, the
fuel pump was a Hilborn "0" which didn't deliver enough fuel for the
longer runs. Everyone told me that running that percentage on 12.5:1
compression ratio wouldn't work and basically they were right, but I got
by with it on the short runs and had a ball. Kinsler tells me that I
could run up to 20% nitro with the pump and nozzles I am using for Alky.
They recommend going 16% larger richer on the bypass jet for each 10% of
nitro. Some day I'm going to try it again. I have five gallons of nitro
that I have been saving for a long time.
Tom, Redding CA - #216 D/CC
Dick J wrote:
>
> Tom,
> I was just cruisin through your website again and
> noticed that you made the notation that you run
> both gas and fuel under a single photo, which got
> me thinking. Do you run both gas and fuel in the
> same motor? Can you do it all at one meet? Or is
> it a complete changeover from one meet to
> another? I have often wondered what the
> differences between fuel and gas motors were. I
> know that gas motors run common CRs in the 10:1 -
> 12:1 area, and alcohol runs something like 15:1.
> What if they are blown motors, CR must be a lot
> lower. What about unblown nitro motor - what
> kind of CR does that run? And last, what about a
> blown nitro motor - what CR do they run?
>
> I guess what I'm asking is: can a single motor,
> either blown or unblown, be built to run both
> gasoline and nitro, or alcohol with just simple
> changes like timing and jets?
>
> =====
> .............................
> ..........Dick J.............
> ......(In East Texas)........
> ..........# 729..............
> ........Roadsters............
> .Hemis and Flatheads Forever.
> .............................
>
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